(CBS NEWS) -- The Republican National Committee won't partner with NBC or CNN on 2016 presidential debates, chairman Reince Priebus warned in letters sent to the two TV networks Monday, unless they agree to pull the plug on recently announced documentary programs about former Secretary of State Hillary Clinton.

Last month, NBC said it would air a four-hour miniseries about the former first lady and top-seeded contender for the Democratic nomination titled, "Hillary;" days later, CNN Films announced its intent to produce a documentary about her. In separate letters to NBC Chairman Robert Greenblatt and CNN President Jeff Zucker, Priebus called each documentary a "thinly veiled attempt at putting a thumb on the scales of the 2016 presidential election."

"This special treatment is unfair to the candidates for the Democratic nomination in 2016 who might compete against Secretary Clinton," Priebus wrote in the letters, specifically naming Vice President Joe Biden, Govs. Martin O'Malley, Andrew Cuomo and John Hickenlooper, and Minnesota Sen. Amy Klobuchar. "Should Clinton compete in the general election," he continued, their programs could also disadvantage the GOP nominee.

"It's appalling to know executives at major networks like NBC and CNN who have donated to Democrats and Hillary Clinton have taken it upon themselves to be Hillary Clinton's campaign operatives," Priebus said in a statement. "I hope Americans will question the credibility of these networks and that NBC and CNN will reconsider their partisan actions and cancel these political ads masked as unbiased entertainment."

Priebus also pointed out the hoopla among Democrats in 2008, when the conservative group Citizens United planned to air a pay-per-view documentary about Clinton on election eve. "And yet they're conspicuously silent now that a major news network will launch a documentary of its own. They must trust that you're doing her a favor," he wrote.

The chairman is seeking a quick turnaround, imposing a nine-day deadline for the networks to decide: "If they have not agreed to pull this programming prior to the start of the RNC's Summer Meeting on August 14," he wrote in the statement, "I will seek a binding vote stating that the RNC will neither partner with these networks in 2016 primary debates nor sanction primary debates they sponsor."

No word yet from NBC or CNN, but mouthpieces from both sides have already started to rally.

A.J. Spiker and Matt Moore, the GOP chairmen for early primary states Iowa and South Carolina, respectively, took to Twitter to announce their backing of Priebus's threat to boycott the networks. And David Plouffe, a former top adviser to President Obama, wrote on the social media site: "Better RNC debate plan. Held in hermetically sealed Fox studio. Avoid exposing swing voters to Crazy S*#t My Nominee Says."